#1. Dortmund miss Hummels
A back injury is keeping Mats Hummels out of the Dortmund team at the moment. He was injured in the 2-2 draw against Eintracht Frankfurt and Lucien Favre's men felt his absence in the second half of that game. They should've been better prepared this time around and were perhaps hoping that Julian Weigl would fill that role well as he did last season.
Although Weigl didn't make any obvious errors, he lacks the leadership and experience that Hummels brings to this Dortmund team. He has been one of the key reasons that Dortmund have been able to come back and keep teams at bay at the start of the season, but without him Dortmund haven't been able to recreate that magic.
Hummels seems to lead by example throwing himself at almost every shot and getting in the way of crosses, but he also provides a reference for the defenders around him to structure their actions and movements. They will hope that he returns to the fray sooner rather than later.